The non-biodegradable pieces of rubbish that wash on to the beaches of southern Europe form only 15 per cent of the total. "Most of it we never see, since 70 per cent sits on the sea bed. And another 15 per cent floats suspended in the water," said Mario Rodriguez, Greenpeace's campaigns director.

Our perception that the Mediterranean is clean is false, campaigners say. "During the holiday season the beaches are cleaned constantly. But, if you stroll along a beach between September and May, you find plastic rubbish all over the place," Mr Rodriguez said.

Of hier, op Geology News:

With about 2000 pieces of discarded plastic per square kilometer, the Mediterranean is thought to have a higher concentration of plastic trash than any other sea. Plastic bottles and plastic bags make up the bulk of this waste. The real problem is that this trash accumulates and does not degrade so the concentration will grow higher over time.